In the oil and gas industry, downhole apparatus including swellable materials which increase in volume on exposure to wellbore fluids are known for use in subterranean wells. For example, swellable wellbore packers are used to seal openhole or lined wells. Such equipment uses swellable elastomers designed to swell on contact with hydrocarbon fluids or aqueous fluids present in the wellbore annulus.
Successful operation of such apparatus is dependent on the well environment and the composition of the well fluids present to initiate swelling. In some wells, the well fluids are deficient at causing the swellable member to expand due to inherent composition or viscosity. This may result in the apparatus failing to operate properly, for example a swellable packer may not provide the required seal. Many dry wells, such as coal bed methane (CBM) wells, simply have insufficient liquid present to use swellable materials.
Furthermore, variations in composition, flow, and viscosity of wellbore fluid, introduce variations into swelling rates of swellable apparatus. This is undesirable in applications which require a carefully controlled and well-understood swelling process.
A problem associated with prior art apparatus and methods is that the expansion parameters of a swellable apparatus may be difficult to predict, guarantee, or control. In existing apparatus and methods there is a lot of time and expense wasted in trying to control the fluid environment for swellable apparatus in attempts to control the swelling parameters. For example, a suitable swellable fluid may be circulated or spotted around the downhole tool. These techniques for predicting, guaranteeing or controlling swellable tools present their own deficiencies and drawbacks, not least that they add complexity and cost to the wellbore operation.